Rustless iron



Patented June 21, 1938 UNITED STATES RUSTLESS IRON William Bell Arness, Baltimore, Md., assignor, by meme cuts, to Bustleas Iron and Steel Corporation, Baltimore, Md., a corporation of Delaware No Drawing. Application July 26, 1935, Serial No. 33,413

5 Claims.

This invention relates to an alloy iron and to corrosion-resistant products or articles of manufacture of the same.

One of the objects of my invention is the pro- 5 vision of a relatively inexpensive alloy iron of wide utility, which readily lends itself to eflicient and economicalhot working into plates, sheets, strips, rcds, bars, wires and tubes of. desired strength, hardness, toughness, ductility and resistance to corrosion and scaling.

Another object is the provision of plates, sheets, wires, strips, bars, and tubes as well as special shapes, corrugated sheet, welded pipe and a variety of die, sand and centrifugal castings 15 which are strong, tough and durable; which are resistant to the progressive corrosion under the various conditions encountered in actual, practical use with a minimum of special preparation of a corrosion-resisting surface, as by special 20 heat-treatment, working or finishing; which readily lend themselves to cutting, drilling, punching, reaming, threading and therlike; which may be riveted, welded, or otherwise fabricated into a variety of articles, structures, appliances 5 or pieces of equipment. 7

Another object is the production of structures,

mining and excavating equipment, chemicalequipment, railway equipment, manufactures and equipment for marine duty, furnace and oven parts and appliances subjected to high temperatures, all of which are lighter in weight than heretofore known carbon or low alloy steel structures of the class indicated and yet which are well adapted to withstand the various physical 35 stresses, temperature changes, climatic conditions and other conditions met in actual, practical use with a minimum of inspection and repair giving maximum reliability and useful life. Other objects will be obvious'in part and in 40 part pointed out hereinafter.

The invention accordingly consists in the combination of elements, mixture of materials and composition of ingredients; in the features of construction and arrangement of parts; and in 45 the several steps and the relation of each ofthesame to one or more of the others as described herein, the scope'of the application of which is indicated in the following claims.

As conducive to asclearer understanding of cer- 50 tain features of my invention it may be noted at this point that various heretofore-known outdoor structures, oil field, mining and excavating equipment, railway equipment, chemical equip ment, structures and appliances for marine servgg ice and a variety of furnace and oven parts and appliances are fashioned from straight carbon and low alloy iron and steel plates sheets, bars, rods, wires and tubes of desired sizes and shapes,

bolted, riveted and welded together. .These various structures, pieces of equipment or products or fabrication are subject to the direct corrosive attack of one or more of many agents encountered in out-door use or in industry or in com merce. For example these structures encounter the attack of the atmosphere under a variety of 10 of various acids, aikalies and salts handled.

Under'the direct attack of the particular corrosive agents encountered, the metal is either locally pitted or there is formed over large sections of the metal a corrosion product. Under the expansion and contraction of the various members,

as well as the shock and vibration encountered in use, portions of the corrosion product scale or slough off and expose the underlying metal. The exposed metal readily corrodes forming a corrosion product which subsequently scales or sloughs away. This action persist's throughout the life of the structure, directly reducing the sectional area, the strength and the ductility of the various structural members and directly reducing the attendant resistance of these members to the load, shock and impact encountered in actual use.

In heretofore known structures, pieces of equipment and products of the character indicated, an

attempt is made to prevent corrosion and loss of the material 'of the various structural members, with the attendant weakening and a reduction inthe life of these members, by coating these 40 members with a zinc, cadmium, chromium or tin plate or by periodically painting the various structural parts with any one of a number of well known oxide paints. Under the many varying conditions met within actual use, however,

the protective plating or coating of paintis soon cracked, scratched or otherwise broken exposing the underlying metal and permitting a direct attack of the metal by the contiguous corrosive medium and the consequent corrosion and weakening of the structure, all as more particularly described above. The periodicalcleaning and plating or painting of suchstructures is costly and is wholly unreliable in the structures' from corrosion. 5

' containers, bins,

They may be sheared. punched, drilled, threaded or otherwise machined. They lend themselves to ready forming as by bending and pressing into a number of special structural shapes. Because of their restricted hardening characteristics they lend themselves to a certain ease in welding, as in, the fabrication of desired structures, articles of commerce and pieces of industrial equipment, all as more particularly pointed out hereinafter.

These products of maufacture are peculiarly resistant to atmospheric attack under a wide variety of weather conditions such as the summer heat, rain, the formation of ice on the products and the like, all in the presence of dirt and dust contained in the atmosphere and various salt, sulphurous or other corrosionfostering agents commonly found in the air about industrial-localities. Furthermore, these products are resistant to the attack of a great number of common acids, alkalies and salts, as appears more fully hereinafter. In addition, the products are well adapted to withstand the shock and vibration and the various stresses of tension, compression and torsion from high summer heat to sub-zero winter cold, as encountered in use, with excellent resistanceto fatigue or failure.

My alloy iron products are particularly adapted to the fabrication of out-door structures such as buildings, bridges, towers, fences and the like where the structures are exposed in whole or in part to changing weather conditions. Likewise, they are well adapted to the production of railway, mining and excavating equipment such as coal washing equiptnent, buckets, machinery parts and hoists. They are well suited to the fabrication of riveted or welded conduits, tanks, bins, hoppers, vats and the like as employed in various chemical, canning and photographic film industries where mildly corrosive liquids, vapor and gases such as nitric acid, ferric sulphate, fruit and vegetable juices, mine waters, soap solutions and photographic developing solutions are handled.

Thesealloy iron plates, sheets, strip, bars, rods, wires and tubes are especially useful in marine duty where lightness in weight coupled with strength and corrosion resistance are required. The tubes andvplate and sheet fabricated into riveted or welded pipes are particularly suitable for surface and sub-surface pipe-lines and culverts, as used in the piping of gas, oil and other corrosion-fostering agents. The bars and rods are useful in the production of sucker rods, pumping equipment, stays and machine parts used in the sour oil fields.

In addition, my alloy iron products are suitable in production or fabrication of furnace and oven parts and appurtenances. They are useful in the production of stays, pins, bolts, supports, frames and trays where combined strength and -resistance to oxidation are desired at temperatures not exceeding about 1200? F.

Where my various alloy iron products are to. be welded as in the fabrication of desired structures, pieces of equipment, or parts of apparatus of the character indicated, certain definite advantages are gained by including in the analysis of the metal one or both of the ingredients nickel and manganese, as appears more fully hereinafter. Good results are achieved where the nickel content amounts to from about .4% up to about 3% with manganese present in usual amounts or where the manganese is present in the amount of from about .4% up to about 3% with nickel present in usual amounts. Best results are achieved, however, where the total amount of the nickel and manganese contents is at least as much as .8% and preferably as much as 1.0%. Ordinarily both nickel and manganese are included in the analysis of the metal in more than the amounts usually encountered, the sum of these ingredients preferably ranging between .8% and 5%, iny alloy iron and the various products of the same preferably analyzing then, approximately 9% to 13% chromium, 4% to 3% nickel, .4% to 3% manganese, .005% to .035% nitrogen, .02% to .0'7% carbon and the balance of the metal substantially all iron.

In the fabrication of a welded structure, article or piece of equipment, electric welding methods are preferably employed, although a good weld is made by means of the oxyacetylene torch. A

welding rod or welding electrode of alloy iron having a chromium content somewhat higher than that of the product welded is used to compensate for the chromium content lost through oxidation during the welding operation. The

carbon content of the welding rod is as low as practicable in order to avoid hardening of the weld metal in cooling. In order to assure a dense weld and one that is free from localized corrosion a small amount of molybdenum is preferably included in the analysis. For example, the welding rods employed analyze apprordmately, 8% to 15% chromium, 3% to 3% molybdenum, 112% to .07% carbon with the balance substantially all iron.

The .weld bead is strengthened and rendered tough without undue hardening in cooling by including in the analysis of the welding rod the further ingredient, nickel, in the amount of about 3% to 3%. This addition furthermore results in' a fine grain structure, gives a ductile weld and in a measureimproves the resistance of the weld to certain corrosive agents. Similarly, certain desirable results are realized by including in the analysis about .3% to 3% of manganese. This ingredient appears to give a cleaner and more fluidweld, directly facilitating the welding operation, and furthermore toughens and strengthens the weld as does the nickel addition.

Best results are achieved where molybdenum,

nickel and manganese are all present in the apwelding products of the character indicated good results are produced employing a rod analyzing approximately 18% chromium, 8% nickel, .0'1 carbon and the balance substantially iron. The bead of weld metal is soft, fine grained in character and is not brittle.

V A soft ductile weld free of grain growth and embrittlement is assured by carefully conducting the welding operation in accordance with knowr'imethodssoasto minimizethetakingup of nitrogen by the weld metal. The presence of an appreciable nitrogen content in the weld bead and metal adjoining the bead serves to harden the metal as it solidifies and cools just as does the presence of an appreciable amount of carbon. By skillful operation of electric arc weldingequipmentoroxy-acetyleneweldingequipment nitrogen contamination or the weld is largely avoided.

Immediately adjacent the weld head there is a zone of metal which has beet. raised to a temperature above the critical point of the alloy iron andis therefore mildlyhardenedin cooling. This hardening, however, is limited by the structural sluggishness of the metal resulting from the additions of nickel and manganese.

Back from the zone of metal immediately adiacent to the weld there is a zone of metal which has reached a temperature just under the critical point. This zoneof metal in cooling is softened somewhat, the softening action being limited, however, by the structural sluggishness of the metal introduced by the presence of nickel and manganese.

After the welding operation is complete in the fabrication of a desired structure, piece of apparatus or piece of equipment, the fabricated structure as desired, may be uniformly reheated in a suitable furnace to a temperature of between 900 to 1400 F. and then permitted to cool. This tempering treatment rel eves the internal stresses introduced as a result of the welding operation and softens both the weld bead and the zones of metal adjoining the weld.

Where the fabricated structure is of such size or for other reasons a complete reheating of the structure is impractical, a satisfactory stress relieving treatment is achieved by locally reheating the actual weld and the zones adjacent the weld by means of a torch. By skillful handling of the torch these regions are brought up to a fairly uniform temperature just beneath the critical point and held at this value sufficiently long to establish a uniform condition in the metal and relieve local streses and hardness. The structure is then permitted to cool and the weld ground or otherwise finished 01! in accordance with known methods. In many instances the weld retains sufficient toughness and ductility,

largely as a result of the nickel and manganese additions in the products welded, to give good results without benefit of a stress relieving treatment. In applications where stress relieving heat-treatment is impracticable metal including about 1% or more each of nickel and manganese is recommended.

In the fabrication of a riveted structure from my 'alloy iron plate, sheet or strip products, an

alloy iron rivet is preferably employed analyzing approximately, 9% to 13%. chromium, 25% to 2% silicon, especially 5% to 2% silicon, .005% to .035% nitrogen, .02% to .0'l% carbon and the balance substantially iron. In general, where the sum of the nitrogen and carbon contents is low the silicon content necessary to achieve the desired results is likewise low although it is advisable to maintain a silicon content at least as much as about five or ten times the sum of thenitrogen and carbon contents or even higher under special circumstances. Such a rivet is especially suitable for hot driving. It is strong, tough, corrosion-resistant and well adapted to withstand impact, shear and other static and dynamic stresses encountered in use. Furthermore, partially because of the high silicon con tent, the rivet hardens but to a very limited extent in cooling during and after driving. In

fact, the driven rivet is sufllciently'soft to permit an ease of chipping or cutting for purposes of removal in no way realized in heretofore known corrosion-resisting rivets of the general character indicated.

Another rivet which is suitable for hot-driving and which is snfllciently soft to be removed by chipping includes or more of the ingredients aluminum, titanium or columbium in small amounts either with or without silicon in the amount indicated. These additions restrict the hardening of the rivet as the metal cools. Such a rivet analyzes approximately 9% to 13% chromium, .03% to .5% of aluminum and/or .10% to .50% of titanium or columbium, .02% to .08% carbon and the balance substantially iron.

Where rivets of increased strength and hardness in the softened condition are desired either one or both of the ingredients nickel and manganese in amounts of approximately .3% to 3% are added to the analysis of the rivet metal. The general corrosion resistance of the rivet is improved by including in the analysis of the rivet metal about .3% to 3% molybdenum. This addition is especially beneficial in preventing local pitting.

While my alloy iron, plate, sheet, strip, bars, rods, wire, special shapes and tubes represent an excellent balance between a desired low manufacturing cost and high physical characteristics, such as strength, hardness, toughness, ductility, impact resistance and corrosion-resistance, coupled with good working, forming and welding properties, certain highly beneficial results are achieved by including in the analysis of the metal the ingredient molybdenum in the amount of from about .3% to 3%.

The presence of molybdenum in the amount of about .3% or more imparts improved corrosionresisting characteristics to the hot-worked plate, sheet, strip, special shapes, bars, rods, wire and tubes in that this addition reduces the susceptibility of these products to a peculiar type of local corrosive attack known as pitting. The molybdenum addition is particularly desirable in products intended for marine duty where the corrosive attack of salt water and salt spray is encountered. .In addition, molybdenum in the amount. indicated is advantageous in lending a certain solidity or soundness to the structure of the metal in which it is included.

Certain other advantages areachieved in my alloy iron or steel products where the ingredient copper is included in the metal in the amount of about .2% to 2%. Copper, in general, acts much in the same way as nickel and because of its comparative cheapness and availability is partially substituted for nickel in the metal. It renders the metal structurally sluggish, materially retarding the rate of phase change during heattreatment and permits the local heating of. the welded areas of welded structures to fully relieve welding stresses. Furthermore, this addition inhibits grain growth during welding and during use of the completed structure, increases the strength of the product and slightly improves the resistance to the corrosive attack of certain acids and salts, especially the chlorides.

Certain other advantages such as increase in strength and a reduction in hardening are obtained by including in the analysis of my alloy iron a small amount of silicon. Good results are ordinarily achieved where the metal includes silicon in the amount of from about .5% to 2% or more. This ingredient is particularly beneficial in improving the heat resistance characteristics of my alloy iron products. I S

An alloy iron. and hot-worked plate, sheet, strip, bars, rods. wire and tubes of the same, including both copper and silicon, a vary good balance of desired physical characteristics, corrosion and heat resistance, good working qualities and good forming and welding properties. Ina 'measure the presence of copper limits the embrittling tendency of the silicon and the presence ofsilicon permits good hot and cold-working characteristics of the copper-containing metal.

Where certain of the hot-rolled alloy iron plates,-sheet, strip, bars and rods are to be machined considerably, any one of the ingredients, sulphur, phosphorus, selenium or tellurium is preferably added in an amount of from about .08% to about 50%. While my alloy iron products possess fairly good machining characteristics without a special addition of one or more of these ingredients, such an addition is definitely beneficial in lending free machining characteristics to the metal and assuring a freedom of the article, part or appurtenance in use without seizing, gelling or binding where a relative motion between two contacting surfaces is encountered.

Thus, it will be seen that there has been provided in this invention comparatively inexpensive alloy iron plates, sheet, strip, bars, rods, wire, tubes and the like, which lend themselves to ready fabrication either by riveting or welding into a wide variety of structures which are well adapted to withstand the various conditions of physical strain and corrosion encountered in actual, prac.-

tical use with a minimum of attention, replacement or repair.

It will be seen that the alloy iron lends itself to highly efllcient and economic production employing available raw materials, including rustless iron scrap in a large measure, and that it is easily handled in the furnace, in the ladle and in the molds. Likewise, it will be seen that the v raw metal readily lends itself to rapid and efficient conversion, as by rolling, drawing and piercing, into products of various shapes and sizes. It will be seen further that converted productsv in the form of plates, sheets, strips, bars, rods, wires and tubes of desired physical characteristics, corrosion-resisting characteristics and working and forming characteristics are achieved with a complete absenceof heat treatment or with a minimum of long and expensive heat-treating operations as desired, with a minimum of cleaning, finishing, polishing and the like and with a minimum outlay of expensive mill, cleaning and finishing equipment.

While, as more particularly indicated above, my alloy iron products are supplied and used in the hot-rolled condition without benefit of along special annealing treatment and without benefit of polishing, it will be understood that where such procedure is found desirable, where cost permits, the iron may be pickled, and used either with or without a special anneal or other heat-treatment as desired. Likewise, it will be understood that where desired, the incorrodible iron plates, sheets, strip, bars and rods coming from the hot mill may be annealed, pickled and cold-rolled giving an improved, incorrodible surface and increased strength and hardness, Similarly, it will .be understood thatwhere ahard product possessing a certain springiness is desired, as in automobile bumpers, metal products coming from the hot-mill may be employed in the air-cooled or air-hardened condition either 'perature or high temperature applications where outdoor atmospheric or mild indoor corrosion conditions are encountered as more particularly indicated above.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiments hereinbefore'set forth it will be understood that all matter described herein is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a composition of matter of the class described, a corrosion-resistant alloy iron of good ductility and weldability which is unsubstantially hardenable by heat-treatment, said alloy iron analyzing approximately, 9 per cent to 13 'per cent chromium, .005 per cent to .035 per cent nitrogen, .02 per cent to .07 per cent carbon and the balance consisting of iron.

2. In articles of manufacture of the class de scribed, corrosion-resistant hot-rolled plate,

which are unsubstantially hardenable by heat treatment, said plate, sheet and strip analyzing approximately, 9 per cent to 13 per cent chromium, .005 per cent to .035 per cent nitrogen, .03 per cent to .07 per cent carbon and the balance consisting of iron.

3. In articles of manufacture of the class described, corrosion-resistant hot-worked bars, rods and wire of good ductility and weldability which are unsubstantially hardenable by heat-treatment, said bars, rods and wire analyzing approximately, 9 per cent to 13 per cent chromium, .005 per cent to .035 per cent nitrogen, .02 per cent to .07 per cent carbon content, and the balance consisting of iron.

4. In a composition of matter of the class described, a corrosion-resistant alloy iron of good ductility and weldability which is unsubstantially hardenable by heat-treatment, said alloy iron analyzing approximately, 9 per cent to -13 per cent chromium, .005 per cent to .025 per cent nitrogen, .02 per cent to .05 per cent carbon and the balance consisting of iron.

5. In manufactures of the class described, a welded corrosion-resisting alloy iron or steel product comprising approximately, 9 per cent to 13 per cent chromium, .005 per cent to .035 per cent nitrogen, .02 per cent to .07 per cent carbon, with the balance consisting of iron. 

